Bioinspired electrochemical artificial muscles with low voltage redox triggering and spontaneous contraction

Skeletal muscle operates through a mechanism in which calcium ions act as a trigger at low electric potentials, followed by contraction powered by adenosine triphosphate hydrolysis. Inspired by this process, we have developed an electrochemical artificial muscle with low-voltage redox triggering and spontaneous contraction. Triggering is achieved by electrochemically charging the muscles at voltages below 0.4 V, which enables I3⁻ injection and subsequent oxidation to I2. Spontaneous muscle contraction then occurs via the reaction I2 + I⁻ → I3⁻, analogous to the role of adenosine triphosphate in skeletal muscle contraction, yet fundamentally distinct from conventional electrochemical artificial muscles. Following this mechanism, pristine carbon nanotube yarn muscles and carbon nanotube yarn muscles modified by quaternary ammonium cations generated contractile strokes of 5.2% and 15.5%, respectively. Moreover, the contracted state can be stably maintained without electrical energy input, and full recovery to the original length is achieved by applying a reverse voltage. Such mechanisms present a promising strategy for the development of energy-efficient artificial muscles. An electrochemical artificial muscle that features low-voltage triggering and spontaneous contraction was developed by utilizing triiodide/iodide redox reactions, mimicking skeletal muscle contraction.